runtime: revert recent Windows crashdump changes

Recent changes to runtime enabled crashdumps, which under some
circumstances apparently might result in memory being uploaded to
Microsoft. A change like this should go through the proper proposals
process where we can discuss how to gate it and what all of its
implications are.

This reverts CL 307372 and its cleanup CL 360617.

Change-Id: If2e74015899d746831da40546c82eacacdf739e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/362454
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/os_windows.go

@@ -40,7 +40,6 @@ const (
 //go:cgo_import_dynamic runtime._LoadLibraryW LoadLibraryW%1 "kernel32.dll"
 //go:cgo_import_dynamic runtime._LoadLibraryA LoadLibraryA%1 "kernel32.dll"
 //go:cgo_import_dynamic runtime._PostQueuedCompletionStatus PostQueuedCompletionStatus%4 "kernel32.dll"
-//go:cgo_import_dynamic runtime._RaiseException RaiseException%4 "kernel32.dll"
 //go:cgo_import_dynamic runtime._ResumeThread ResumeThread%1 "kernel32.dll"
 //go:cgo_import_dynamic runtime._SetConsoleCtrlHandler SetConsoleCtrlHandler%2 "kernel32.dll"
 //go:cgo_import_dynamic runtime._SetErrorMode SetErrorMode%1 "kernel32.dll"
@@ -94,7 +93,6 @@ var (
 	_PostQueuedCompletionStatus,
 	_QueryPerformanceCounter,
 	_QueryPerformanceFrequency,
-	_RaiseException,
 	_ResumeThread,
 	_SetConsoleCtrlHandler,
 	_SetErrorMode,
@@ -122,7 +120,6 @@ var (
 	_AddVectoredContinueHandler,
 	_LoadLibraryExA,
 	_LoadLibraryExW,
-	_WerSetFlags,
 	_ stdFunction
 
 	// Use RtlGenRandom to generate cryptographically random data.
@@ -257,7 +254,6 @@ func loadOptionalSyscalls() {
 	_AddVectoredContinueHandler = windowsFindfunc(k32, []byte("AddVectoredContinueHandler\000"))
 	_LoadLibraryExA = windowsFindfunc(k32, []byte("LoadLibraryExA\000"))
 	_LoadLibraryExW = windowsFindfunc(k32, []byte("LoadLibraryExW\000"))
-	_WerSetFlags = windowsFindfunc(k32, []byte("WerSetFlags\000"))
 	useLoadLibraryEx = (_LoadLibraryExW != nil && _LoadLibraryExA != nil && _AddDllDirectory != nil)
 
 	var advapi32dll = []byte("advapi32.dll\000")

src/runtime/panic.go

@@ -1002,11 +1002,6 @@ var runningPanicDefers uint32
 // panicking is incremented and decremented atomically.
 var panicking uint32
 
-// tracebackprinted is zero before gopanic() prints the traceback. After
-// traceback is printed, it sets to 1 so that the subsequent exception handler
-// won't print the traceback again.
-var tracebackprinted uint32
-
 // paniclk is held while printing the panic information and stack trace,
 // so that two concurrent panics don't overlap their output.
 var paniclk mutex
@@ -1050,9 +1045,6 @@ func fatalthrow() {
 		startpanic_m()
 
 		if dopanic_m(gp, pc, sp) {
-			// At this point, traceback has already been printed.
-			// Set tracebackprinted to 1 to avoid printing traceback again
-			tracebackprinted = 1
 			// crash uses a decent amount of nosplit stack and we're already
 			// low on stack in throw, so crash on the system stack (unlike
 			// fatalpanic).
@@ -1094,9 +1086,6 @@ func fatalpanic(msgs *_panic) {
 	})
 
 	if docrash {
-		// At this point, traceback has already been printed.
-		// Set tracebackprinted to 1 to avoid printing traceback again
-		tracebackprinted = 1
 		// By crashing outside the above systemstack call, debuggers
 		// will not be confused when generating a backtrace.
 		// Function crash is marked nosplit to avoid stack growth.

src/runtime/signal_windows.go

@@ -22,38 +22,6 @@ func disableWER() {
 	stdcall1(_SetErrorMode, uintptr(errormode)|SEM_FAILCRITICALERRORS|SEM_NOGPFAULTERRORBOX|SEM_NOOPENFILEERRORBOX)
 }
 
-// isWin7 returns true on Windows 7. Otherwise it returns false.
-//
-//go:nosplit
-func isWin7() bool {
-	var maj, min, build uint32
-	stdcall3(_RtlGetNtVersionNumbers, uintptr(unsafe.Pointer(&maj)), uintptr(unsafe.Pointer(&min)), uintptr(unsafe.Pointer(&build)))
-	return maj < 6 || (maj == 6 && min <= 1)
-}
-
-// enableWERNoUI re-enables Windows error reporting without fault reporting UI.
-//
-// This is marked nosplit since it is used during crash.
-//
-//go:nosplit
-func enableWERNoUI() bool {
-	if _WerSetFlags == nil {
-		return false
-	}
-
-	// Disable Fault reporting UI
-	const (
-		WER_FAULT_REPORTING_NO_UI = 0x0020
-	)
-	if stdcall1(_WerSetFlags, WER_FAULT_REPORTING_NO_UI) != 0 {
-		return false
-	}
-
-	// re-enable Windows Error Reporting
-	stdcall1(_SetErrorMode, 0)
-	return true
-}
-
 // in sys_windows_386.s and sys_windows_amd64.s
 func exceptiontramp()
 func firstcontinuetramp()
@@ -140,7 +108,6 @@ func exceptionhandler(info *exceptionrecord, r *context, gp *g) int32 {
 		// Don't go through any more of the Windows handler chain.
 		// Crash now.
 		winthrow(info, r, gp)
-		exit(2)
 	}
 
 	// After this point, it is safe to grow the stack.
@@ -229,20 +196,6 @@ func lastcontinuehandler(info *exceptionrecord, r *context, gp *g) int32 {
 	}
 
 	winthrow(info, r, gp)
-
-	_, _, docrash := gotraceback()
-	if docrash {
-		// Windows 7 apears to ignore WER_FAULT_REPORTING_NO_UI
-		// WerSetFlags API flag. So do not call enableWERNoUI
-		// on Windows 7.
-		if !isWin7() {
-			// trigger crash dump creation
-			if enableWERNoUI() {
-				return _EXCEPTION_CONTINUE_SEARCH
-			}
-		}
-	}
-	exit(2)
 	return 0 // not reached
 }
 
@@ -250,6 +203,11 @@ func lastcontinuehandler(info *exceptionrecord, r *context, gp *g) int32 {
 func winthrow(info *exceptionrecord, r *context, gp *g) {
 	_g_ := getg()
 
+	if panicking != 0 { // traceback already printed
+		exit(2)
+	}
+	panicking = 1
+
 	// In case we're handling a g0 stack overflow, blow away the
 	// g0 stack bounds so we have room to print the traceback. If
 	// this somehow overflows the stack, the OS will trap it.
@@ -271,16 +229,18 @@ func winthrow(info *exceptionrecord, r *context, gp *g) {
 	_g_.m.throwing = 1
 	_g_.m.caughtsig.set(gp)
 
-	level, _, _ := gotraceback()
+	level, _, docrash := gotraceback()
 	if level > 0 {
-		// only print traceback when it hasn't been printed
-		if tracebackprinted == 0 {
 		tracebacktrap(r.ip(), r.sp(), r.lr(), gp)
 		tracebackothers(gp)
-			tracebackprinted = 1
-		}
 		dumpregs(r)
 	}
+
+	if docrash {
+		crash()
+	}
+
+	exit(2)
 }
 
 func sigpanic() {
@@ -352,17 +312,14 @@ func signame(sig uint32) string {
 
 //go:nosplit
 func crash() {
-	// When GOTRACEBACK==crash, raise the same exception
+	// TODO: This routine should do whatever is needed
-	// from kernel32.dll, so that Windows gets a chance
+	// to make the Windows program abort/crash as it
-	// to handle the exception by creating a crash dump.
+	// would if Go was not intercepting signals.
-
+	// On Unix the routine would remove the custom signal
-	// Get the Exception code that caused the crash
+	// handler and then raise a signal (like SIGABRT).
-	gp := getg()
+	// Something like that should happen here.
-	exceptionCode := gp.sig
+	// It's okay to leave this empty for now: if crash returns
-
+	// the ordinary exit-after-panic happens.
-	// RaiseException() here will not be handled in exceptionhandler()
-	// because it comes from kernel32.dll
-	stdcall4(_RaiseException, uintptr(unsafe.Pointer(&exceptionCode)), 0, 0, 0)
 }
 
 // gsignalStack is unused on Windows.